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African amaranth, muricate amaranth

fringe amaranth, fringe pigweed

Habit Plants annual or short-lived perennial, glabrous or slightly pubescent near tips. Plants glabrous.
Stems

ascending or prostrate, much-branched from stout rootstock, 0.1–0.4 m.

erect or with lateral branches ascending, usually branched from base, main and lateral stems sparingly branched or simple, 0.3–0.7(–1) m.

Leaves

petiole to 1/2 as long as blade;

blade linear to narrowly lanceolate, 1.5–8 × 0.2–0.5(–1) mm, base tapering, margins entire, plane to undulate, apex obtuse and often emarginate.

short-petiolate;

petiole 1/4–1/2 as long as blade;

blade linear to narrowly lanceolate, (1–)2–6(–10) × 0.1–0.5(–1) cm, base narrowly cuneate, margins entire, plane, apex acute to mucronulate.

Bracts

of pistillate flowers linear, 0.7–1.2 mm, 1/2–2/3 as long as tepals.

of pistillate flowers ovate to ovate-lanceolate, 1–1.8 mm, shorter than tepals, about 1/2 or less as long as tepals.

Inflorescences

terminal, compact pyramidal panicles and axillary glomerules, erect or reflexed, green, leafless at least distally.

mostly axillary clusters scattered from base to apex of plants, distally condensed in lax, unbranched, almost leafless, slender, terminal spikes, interrupted.

Staminate flowers

intermixed with pistillate or at tips of inflorescences;

tepals 5;

stamens 5.

tepals 5, apex obtuse;

stamens (2–)3.

Pistillate flowers

tepals 5, narrowly oblanceolate, not clawed, equal, 1.5–2 mm, apex obtuse or subacute;

style branches erect;

stigmas 3.

tepals 5, reflexed, fan-shaped to broadly spatulate, clawed, equal or subequal, 1.5–3.3 mm, margins fimbriate or denticulate, apex much expanded and obtuse;

style branches erect to ± spreading;

stigmas 3(–4).

Seeds

black, lenticular, 1–1.2 mm diam., semiglossy.

black or dark reddish brown, lenticular to broadly lenticular, 0.8–1 mm diam., shiny, smooth.

Utricles

compressed, subglobose, 1.7–2 mm, ± equaling or slightly exceeding tepals, muricate, indehiscent.

subglobose to obovate, 1.2–2 mm, shorter than tepals, rugose to nearly smooth, dehiscence regularly circumscissile.

2n

= 34.

Amaranthus muricatus

Amaranthus fimbriatus

Phenology Flowering summer–fall. Flowering summer–fall (in arid regions mostly after summer rains).
Habitat Waste places, on ballast Sandy, gravelly slopes, washes, semideserts, disturbed habitats
Elevation 0 m (0 ft) 500-1700 m (1600-5600 ft)
Distribution
from FNA
AL; s South America (Argentina, Paraguay, Uruguay) [Introduced in North America; introduced in s Europe, s Africa, Australia, and other regions]
[BONAP county map]
from FNA
AZ; CA; NM; TX; UT; n Mexico
[WildflowerSearch map]
[BONAP county map]
Discussion

The vernacular name “African amaranth” is sometimes used for this species; it is a misnomer; the species is native to South America and naturalized in Africa.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Two varieties of Amaranthus fimbriatus have been recognized: var. fimbriatus, with tepals fimbriate at the apex, and var. denticulatus (= A. venulosus S. Watson), with denticulate or crenulate tepals. The latter is reported from Arizona and adjacent northern Mexico; it probably occurs more widely.

A related species, Amaranthus chihuahuensis S. Watson, which occurs in Mexico (Chihuahua and Oaxaca), was reported from trans-Pecos Texas, but no reliable specimens were seen by C. F. Reed (1969b). The presence of that species in the United States needs confirmation, and its taxonomic identity remains obscure.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 4, p. 431. FNA vol. 4.
Parent taxa Amaranthaceae > Amaranthus > subg. Albersia Amaranthaceae > Amaranthus > subg. Amaranthus
Sibling taxa
A. acanthochiton, A. albus, A. arenicola, A. australis, A. blitoides, A. blitum, A. californicus, A. cannabinus, A. caudatus, A. crassipes, A. crispus, A. cruentus, A. deflexus, A. dubius, A. fimbriatus, A. floridanus, A. graecizans, A. greggii, A. hybridus, A. hypochondriacus, A. obcordatus, A. palmeri, A. polygonoides, A. powellii, A. pumilus, A. retroflexus, A. scleropoides, A. spinosus, A. tamaulipensis, A. thunbergii, A. torreyi, A. tricolor, A. tuberculatus, A. viridis, A. viscidulus, A. watsonii, A. wrightii
A. acanthochiton, A. albus, A. arenicola, A. australis, A. blitoides, A. blitum, A. californicus, A. cannabinus, A. caudatus, A. crassipes, A. crispus, A. cruentus, A. deflexus, A. dubius, A. floridanus, A. graecizans, A. greggii, A. hybridus, A. hypochondriacus, A. muricatus, A. obcordatus, A. palmeri, A. polygonoides, A. powellii, A. pumilus, A. retroflexus, A. scleropoides, A. spinosus, A. tamaulipensis, A. thunbergii, A. torreyi, A. tricolor, A. tuberculatus, A. viridis, A. viscidulus, A. watsonii, A. wrightii
Synonyms Euxolus muricatus Sarratia berlandieri var. fimbriata, A. fimbriatus var. denticulatus
Name authority (Moquin-Tandon) Hieronymus: Pl. Diaph. Fl. Argent., 227. (1882) (Torrey) Bentham ex S. Watson: in W. H. Brewer et al., Bot. California 2: 42. (1880)
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